If you have ordered the Samsung Galaxy S9, you will receive the device from a contract extension or if you want to buy it in the shop, please check whether your currently used Sim card also fits into the Sim card slot of the S9 or the S9 Plus. Why is this question important?
If you have an older Sim card in standard or micro format, it doesn't fit!
This Sim card format uses the Samsung Galaxy S9
Because the Samsung Galaxy S9 uses a sim card slot, in which only one Nano Sim card fits. If you still have an older SIM card format, you will have to convert the SIM card into a nano format or order it from your mobile phone provider:
How to get a Nano Sim card:
Sim card punching
You can also purchase a Sim card punch or "punch". This can then be used to create a Nano Sim card from a standard or micro sim card using a template. This is easy and inexpensive.
Such Sim card punchers are available on Amazon for example.
Use perforation, if available
Many Sim cards that are in circulation have a perforation that makes it easy to push a Nano Sim card out of the existing one. If you have such a card, just press the Nano Sim card and insert it into your smartphone.
Request Nano Sim from mobile phone provider
Another possibility is to request a new SIM card from your mobile operator. This is usually associated with costs around 20-25$. The shipping of the Sim Card is fast and you will receive the card usually within 3 working days.